Research Projects

Rationale of the Research: During cell lineage specification, transcriptional activation of cell type-specific genes and silencing of lineage non-specific genes are essential. Disruptions in these processes underlie many developmental disorders and cancers. Recent studies have linked mutations in heterochromatin modifying enzymes responsible for H3K9me and DNA methylation to these diseases. These modifiers are traditionally associated with silencing constitutive heterochromatin at repetitive DNA elements, but recent evidence highlights their crucial role in stabilizing cell fate by silencing lineage non specific genes during development. Despite the significance of H3K9me deposition in regulating lineage-specific gene expression, how these heterochromatin modifiers are targeted to specific gene regulatory elements remains poorly understood. Additionally, how disruptions in these pathways contribute to disease mechanisms remains an open question. To address this, we recently identified Zfp462 as a sequence-specific factor that targets H3K9me containing heterochromatin to lineage controlling regulatory sequences by recruiting the G9A/GLP histone methyltransferase complex, opening new avenues for exploring these mechanisms. The human ortholog, ZNF462, is a high confidence neurodevelopmental disorder risk gene linked to Weiss Kruszka Syndrome. Systematic analysis of the Zfp462/ZNF462 function will provide crucial insights into chromatin mediated gene regulation and its role in neurodevelopmental diseases. Hypothesis and models to be tested: 1) In Weiss-Kruszka Syndrome (WKS) disease-modelled mESCs with patient-specific nonsense mutations, we observed the persistence of mutant transcripts, suggesting the possibility of truncated protein production. We will test whether the truncated protein forms abnormal protein complexes, leading to mis-regulation of gene expression. 2) ZFP462/ZNF462 contains a PBX1 binding domain, confirmed by immunoprecipitation in differentiated mouse cells and Xenopus tissues. However, in mESC protein extracts, we did not observe an interaction between ZFP462 and transcriptional activator PBX1. We hypothesize that in pluripotent cells, ZFP462 interacts with G9A/GLP to function as a repressor. Upon neuronal differentiation ZFP462 binds PBX1, disrupting the G9A/GLP interaction and switching its role to an activator. 3) ZFP462 regulates neuronal lineage specification by silencing mesoendodermal regulatory regions via heterochromatin recruitment in mice. Genome-wide analysis of ZNF462 in hESCs revealed its binding to CTCF sites and endodermal regulatory loci, indicating an acquired function in humans. We propose that ZNF462 has evolved unique roles in humans, regulating lineage-specific loci and CTCF-bound sites that impact lineage specification and genome organization.